EP0710526B1

EP0710526B1 - Spectacle lens and manufacturing method thereof

Info

Publication number: EP0710526B1
Application number: EP95307765A
Authority: EP
Inventors: Susumu Hagiwara; Makoto Fukuyama; Satoru Dainimiyamaedairaryo Kimura
Original assignee: Nikon Corp; Nippon Kogaku KK
Current assignee: Nikon Corp
Priority date: 1994-10-31
Filing date: 1995-10-31
Publication date: 2001-12-12
Anticipated expiration: 2015-10-31
Also published as: DE69524544D1; DE69524544T2; US5790232A; CA2160192A1; EP0710526A1

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a manufacturing method of and a manufacturing system for manufacturing and supplying a spectacle lens optimal to a user in accordance with a prescription of the user and also a spectacle lens manufactured and supplied thereby.

Related Background Art

Generally, a shape of a lens used for a spectacle is round before being machined, and an edge thickness thereof is fixed. For insetting the lens in a spectacle frame, the lens has to be machined in accordance with frame dimensions. Further, recently there are increasingly demands for decreasing a weight of the spectacles and thinning the lenses, and there is also an attempt at an improvement for insetting lenses that are as thin as possible in the spectacle frames (see for example EP-A-0 061918, DE-A-4221 377, DE-A-3801 384). Under such circumstances, a machining method known as an outer shape designation machining is employed as a measure for the improvement. According to this method, the user chooses a spectacle frame, a minimum outer diameter of the lens that can be inset in this frame is measured and a pre-machining lens having an outer diameter satisfying the minimum outer diameter is selected and then machined in accordance with the frame dimensions. The outer shape designation machining will be explained with reference to Fig. 6. As illustrated in Fig. 6, in the case of a (+) lens, a lens that is smaller in terms of its central thickness, edge thickness and weight is obtained by selecting and machining a lens having a minimum outer diameter of 50 mm enough to be inset in the frame than by selecting a pre-machining lens having an outer diameter of, e.g., 65 mm and thereafter machining an edge portion of the lens in accordance with dimensions of the spectacle frame. In general, this work is conducted in an optician's shop. Further, there was a machining method based on an ET (Edge Thinning) method as other machining method. This method is effective in an astigmatism lens. Moreover, there could be recently done an accurate measurement of a round shape of the lens inset in the spectacle frame mechanically traced by a device known as a tracer. When the exact round shape is measured, it is possible to machine the lens exhibiting optimum properties such as, e.g., a lens edge thickness and a lens central thickness. According to the lens machined by this method, the thinnest lens corresponding to the prescription of the user can be machined at present (however, excluding a lens involving the use of a base material exhibiting a high refractive index). Then, the following is a system proposed. The device known as the tracer for mechanical tracing is installed in the optician's shop, and the round-shape data and the data on the prescription such as a lens power of the user are transmitted to a lens maker for actually machining the lens in the round shape, wherein the machining thereof is performed. The thus machined lens is sent back to the optician's shop. According to this system, the optician's shop is not required to effect the round shape machining and the bevel edge machining that have hitherto been conducted in the optician's shop. It is therefore feasible to omit technical training such as acquiring an optician's skill of a worker in the optician's shop.
With these improvements, the lens exhibiting the optimum properties corresponding to the nature of the eyes of the user can be manufactured.
A variety of improvements described above make it possible to manufacture the lens corresponding to the user and thin the lens down to an extent optimal to the user. However, the prescription for the lens powers of the right and left lenses largely differ depending on the user. In this case, if each of the right and left lenses is manufactured by the above methods, it may happen that the lenses are inset in the spectacle frame in a state where the central thicknesses and the edge thicknesses or the lens curves of the right and left lenses are different. A problem arises, wherein the spectacles in this state have ill-balanced right and left lenses, resulting in an undesirable outer shape (see Figs. 7A and 7B). Further, if the imbalanced right and left lenses are used for two-point frame spectacles which have recently gained an increased number of users, a problem is that especially a difference in the edge thickness between the right and left lenses becomes conspicuous when using such imbalanced right and left lenses.

SUMMARY OF THE INVENTION

It would be desirable to provide well-balanced spectacles with almost no difference in terms of lens curve and thickness between right and left lenses even when there is a difference in lens power between the right and left lenses.
This problem is solved by a method according to claim 1 and an apparatus according to claim 10.
Embodiment of the present invention are set out in the appended claims.
Balance adjustments between the lens curves, the central thicknesses and the edge thicknesses of the right and left lenses of a pair of spectacle lenses may be performed on the basis of an accurate measurement of the round shape by use of a tracer and a further balance adjustment may be made between the frame curve (curve of the spectacle frame) and the lens curve. When measuring the round shape by the tracer, it is possible to obtain the data for manufacturing a thin lens optimal to a prescription and a shape of the spectacle frame of the user. A lens thickness of a relatively thin lens may be made to approximate to a lens thickness of a relatively thick lens with respect to the right and left lenses while keeping the thinning of the lenses on the basis of the data on the thinnest lens that can be manufactured by use of this tracer in the lens developed based on such an idea that the right and left spectacle lenses have hitherto been separately manufactured and respectively thinned one-sidedly. With respect to an idea contrary to the conventional idea aiming at thinning the lenses one-sidedly, even the relatively thickened lens has the minimum lens thickness measured by the tracer on the basis of the prescription, etc. Hence, substantially even when increasing the thickness of the relatively thin lens, the degree of thinning is not retrogressed under that of the conventional lens. Accordingly, the thinner lens than by the prior art can be obtained, and, further, it is possible to manufacture the well-balanced lenses in terms of the lens curves and the lens thicknesses of the right and left lenses.
Moreover, a basic lens material used in an embodiment at the invention of the present application involves the use of a material exhibiting a high refractive index (n_d = 1.5 to 1.7), whereby the thinner lens can be manufactured. Then, usable materials for the lens are polymethyl methacrylate and polymer thereof, polycarbonate, diethylene glycol bis allyl carbonate, (bromide) bisphenol A di(metha)acrylate polymer and copolymer thereof, polymer of urethane modified monomer of (bromide) bisphenol A mono(metha)acrylate and copolymer thereof, polyester and unsaturated polyester, acrylonitrile-sthyrene copolymer, vinyl chloride, polyurethane and epoxy resin.
The above and other objects, features and advantages of the present invention will be explained hereinafter and may be better understood by reference to the drawings and the descriptive matter which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flowchart showing procedures of measuring a shape of a spectacle frame;
Fig. 2 is a flowchart showing procedures of performing a curve adjustment according to the present invention;
Fig. 3 is a flowchart showing procedures of performing a thickness adjustment of right and left lenses according to the present invention;
Fig. 4 is a conceptual diagram illustrating a measurement position when effecting the thickness adjustment of the right and left lenses in accordance with this embodiment;
Fig. 5 is a schematic diagram illustrating a supply system of the spectacle lenses in accordance with this embodiment;
Fig. 6 is a conceptual diagram showing a method of manufacturing the lens on the basis of a designation of an outer diameter in the prior art; and
Figs. 7A and 7B are conceptual diagrams of sections of a pair of right and left spectacle lenses manufactured by the conventional manufacturing method as viewed from above in the horizontal direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1) Trace of Spectacle Frame

According to the present invention, at first, a round shape of a frame is measured by a conventionally practiced method involving the use of a tracer. Fig. 1 shows procedures of measuring a lens curve (LC) and a frame curve (FC) by use of the tracer. To start with, in step 1 (S1), a round shape (r, ) of the spectacle frame is measured. In the case of two-point frame spectacles, a shape of a mold plate is measured. Further, a peripheral length of the round shape and the frame curve are calculated. Next, a type of the lens is determined based on these items of data (S2). Specified subsequently are a prescription about a lens power, a pupil distance and a height at the center of pupil with respect to the frame, machining data about a position of a far center and a small lens in the case of a progressive focus lens, a bevel edge position, a type of the bevel edge and a matter of whether or not the balance adjustment of the lens curves of the right and left lenses is performed (S3). Previously measured r,  are converted into values of r', ' which takes the optical center into consideration from the prescription on the basis of those items of data. These items of data are inputted to a curve balance adjusting unit. The curve balance herein includes a balance adjustment of the lens curves of the right and left lenses and a balance adjustment of the frame curve and the lens curve.

2) Curve Balance Adjustment

A curve balance adjustment will be explained with reference to a flowchart of Fig. 2.
To begin with, lens curves (LCr, LCl) of an R1 surface are selected based on the data processed in steps S1 to S4. Next, right and left bevel edge curves (YCr, YCl) are determined based on this item of lens curve data.
Subsequently, a difference between this item of bevel edge curve data and frame curve data (FC) as a fiducial item of data inputted beforehand is calculated. If a value of the difference calculated herein is not more than a specified value (e.g., a 1.0-curve), a determination is made that there is no necessity for correcting a balance between the bevel edge curve and the frame curve, and the operation proceeds to a process of making a comparison between next LCr and LCl. If the difference between the bevel edge curve and the fiducial frame curve data (FC) is larger than the 1.0-curve, however, a shifting process is performed so that the lens curves LCr, LCl approximate the fiducial data FC. There are prepared several types of lenses each having a certain lens curve so that the lens curve changes stepwise. The term "shift" used herein connotes a stepwise approximation to the fiducial frame curve. In this shift, after only one shifting process has been effected by one operation, the data thereof is transmitted to a processing unit where the bevel edge curve is recalculated. This operation is repeated till the difference therebetween becomes equal to or smaller than ±1.0-curve (k). Further, the number of repetitions may be limited. Moreover, as a matter of course, the specified value ±1.0-curve (k) may be varied. The processes explained so far are those of adjusting the balance between the bevel edge curve and the frame curve.
Adjusted next is a balance between the right-and-left lens curves.
When the difference between the bevel edge curve (YC) and the fiducial data FC falls within the specified value, a difference in terms of the curve value between the right and left lens curves (LCr, LCl) of the R1 surface is compared with the specified value. If the difference herein falls within the specified value (e.g., less than the 1.0-curve), there are terminated the balance adjustments between the frame curve and the lens curve and between the right-and-left lens curves, and it follows that optimum values of the lens curve and the bevel edge curve are outputted. If the difference in the lens curve value between the right and left lenses is outside the specified value (e.g., 1.0 or greater curve), there is made a comparison in terms of shift quantity between the right and left lenses on the basis of the left lens. More specifically, a difference between the number of shifts of the left lens and the number of shifts of the right lens is calculated. If a calculated flag (the number of shifts) is larger than 0, the shift quantity becomes larger by shifting the value of the lens curve of the left lens than by making the right-and-left balance adjustment while shifting the value of the lens curve of the right lens. Whereas if the flag is smaller than 0, this indicates that the shift quantity of the right lens increases. Based on this, there is determined which is the optimum, the right lens or the left lens, to shift in the case of adjusting the balance between the right-and-left lens curves and the balance between the frame curve and the lens curve. Then, the operation goes back again to the bevel edge curve calculating unit, wherein the processing is repeated.
With those processes, there are obtained the balance-adjusted lens data between the lens curve and the bevel edge curve with respect to the right and left lenses or the spectacle frame. Thereafter, a lens curve of an R2 surface is determined (unillustrated). Further, the processing procedures which follow may also be taken as another processing method. At first, a lens curve of the R1 surface of the right lens is selected based on the data on the user's prescription, etc. Next, a lens curve that is most approximate to the frame curve is obtained within such a range that an optical problem like an aberration does not arise. Subsequently, the same processing as the right lens is performed on the left lens. Then, the balance between the frame curve and the lens curve can be adjusted by obtaining a difference in the lens curve between the right and left lenses.

3) Thinning of Lens

After the processing stated in the item 2), ETs (edge thicknesses) of the right and left lenses on the round-shape data (r', ') are calculated based on central thicknesses of the right and left lenses (S5). Then, the central thicknesses satisfying a minimum ET condition for every lens power of the right and left lenses are determined (S6). Next, whether the bevel edge is provided or not is determined (S7). When providing the bevel edge, the central thicknesses satisfying the minimum ET condition is determined in accordance with step S6, and the operation proceeds to the unit for adjusting the balance between the right-and-left lens thicknesses. Whereas if no bevel edge is provided, whether the frame is the two-point frame or not is determined (S8). If not the two-point frame, it follows that a groove is formed in a lens edge surface. A minimum ET (e.g., 2 mm) at this time is specified, and whether an ET is larger than this specified value or not is determined (S9). If the ET is larger than the specified value, the central thickness is set as the minimum ET condition is satisfied, and the operation proceeds to a processing step of a thickness balance adjustment. Whereas if the ET is smaller than the specified value, the central thickness is determined according to the specified value (e.g., 2 mm). When determining that the spectacles are classified as two-point frame spectacles in step S8, a minimum edge thickness (HT) in a holing position is specified in step S10. If the minimum edge thickness is larger than this specified value, an adjustment is made to meet a minimum edge thickness condition, and the operation proceeds to a next step of adjusting a thickness balance between the right and left lenses. Whereas if the minimum edge thickness is smaller than the specified value, the adjustment is still made to meet the minimum edge thickness condition.
4) Next, a lens thickness balance adjustment unit performs a balance adjustment relative to the thicknesses of the right and left lenses on the basis of this item of data and the prescription data. The lens thickness balance adjustment will be explained with reference to Fig. 3.
Central thicknesses (R_CT, L_CT) and edge thicknesses (R_max, L_max and R_min, L_min) of the right and left lenses as shown in Fig. 4 are determined from the lens curves obtained by the curve balance adjustment unit as well as from the prescription. These values are inputted to the lens thickness balance adjustment unit, and the lens thickness adjustment unit calculates values of the lens thicknesses to be adjusted based on the following formula:
when the right lens is thin, R'CT = RCT + Rmax - Lmax × α
and when the left lens is thin, L'CT = LCT + Rmax - Lmax × α where α: the factor of a complementary thickness.
In the case of a (+) lens, α = 0.8, but in the case of a (-) lens, α = 0.4. However, as in the case of the following formula, a determination is that the complementary thickness is not required. α × Rmax - Lmax ≤ 0.3
An arbitrary numerical value may be freely set instead of 0.3 in the formula 2.
With the processes effected by the above-described curve balance adjusting unit and lens thickness balance adjustment unit, the set values of the lens curve, the frame curve and the lens thicknesses (central thickness, edge thickness) are outputted. Then, a semi material having a determined lens curve is employed and at first machined in the round shape measured by the tracer on the basis of these items of data. The semi material is then machined based on the data obtained from the respective units by a finishing machining, thereby obtaining a lens. This finishing machine may be constructed as a system which is connected to the curve balance adjustment unit and the lens thickness balance adjustment unit, receives the data thereof and automatically performs machining; or alternatively, the machining is carried out by a machine operator operating the finishing machine in accordance with the respective items of data.

[Embodiment 2]

Further, embodying to the present invention, as illustrated in Fig. 5, a data transmitting apparatus is installed in an optician's shop 1, while data receiving apparatus is installed in a lens machining yard, and these two apparatuses can be connected via a public communications line (e.g., a VAL), etc. Provided therein are an online terminal computer 2 for the optician's shop 1 and a frame shape measuring instrument 3 known as a tracer. The terminal computer 2 is equipped with an input device through a keyboard and a CRT screen display unit and is connected to the public communications line. An item of spectacle lens data, a prescription, etc. are inputted to the terminal computer 2 from the built-in keyboard input device. An item of measured and calculated spectacle frame data is also inputted to the terminal computer 2 from the frame shape measuring instrument 3. Those items of data are transferred online to the machining yard via the public communications line.
A main computer 4 incorporates a spectacle lens machining design program, a bevel edge machining design program, etc. and, on the basis of the inputted data, calculates a lens shape including a bevel edge shape. The main computer 4 then transmits an arithmetic result thereof back to the terminal computer 2 via the public communications line and makes the built-in screen display to display the arithmetic result. The arithmetic result is then transmitted to respective terminal computers 6, 7 in a factory 5 via the LAN. A polishing machine 8 is connected to the terminal computer 6. The terminal computer 6 controls the polishing machine 8 in accordance with the arithmetic result transmitted from the main computer 4 and finishes a curvature of the rear surface of the lens, the upper surface of which is previously machined. An NC lens grinding machine 9 is connected to the terminal computer 7 and performs lens edge machining and bevel edge machining in accordance with the arithmetic result transmitted from the terminal computer 7. The curve adjustment unit and the lens thickness control unit according to the present invention are incorporated into the main computer. The optician's shop and the machining factory are connected through the thus constructed system. Accordingly, the optician's shop is capable of ordering the balance-adjusted lens between the lens thicknesses and between the lens curves of the right and left lenses as well as between the frame curve of the spectacle frame and the lens curve of the lens from the lens factory simply by transmitting the respective items of data to the machining factory. It follows that the spectacles can be fabricated simply by insetting the lenses in the spectacle frames. As a matter of course, in the factory, the machining can be done even when a man participates in the machining on the basis of the data transmitted from the optician's shop without connecting each terminal to the finishing machine.
The lens as manufactured according to the present invention may be finished by separately performing the lens curve adjustment of the right and left lenses, the lens thickness adjustment of the right and left lenses and the adjustment between the lens curve and the frame curve or by performing these adjustments in combination.
As discussed above, even when there is a difference in the lens thickness between the right and left lenses, the well-balanced spectacles can be obtained, wherein there is almost no difference both in the lens curve and in the thickness between the right and left lenses. A well-shaped lens is thereby obtained. Further, the balance in terms of the thicknesses of the right and left lenses is adjusted, and, hence, there is eliminated the difference in weight between the right and left lenses. This in turn eliminates both a deviation of the spectacle due to the difference in terms of the lens weights and an uncomfortable feeling caused when wearing the spectacles. Particularly in the case of the two-point frame type spectacles with their edge thicknesses being conspicuous, there is a large effect produced by eliminating the difference in the edge thickness between the right and left lenses. Moreover, in the lens manufactured according to the present invention, the round shape is at first measured accurately, and the machining is carried out on the basis of such a condition that the thinnest lens in terms of design can be manufactured. Hence, there is obtained the spectacle lens in which the lens machined according to the present invention is small both in weight and in thickness. Further, the balance between the frame curve, the lens curve and the bevel edge curve is adjusted, and, therefore, a load on the lens after being insert in the frame is decreased, and a life-span of the spectacle elongates. In the case of using the progressive lens, an optimal prism thinning quantity is applied in consideration of the layout and the shape of the spectacle frame, whereby the well-balanced, light-weight and thin lens can be manufactured. Further, when the optician's shop is connected via the communications network, etc. to the machining yard, the optician's shop measures the round shape by use of the tracer and also a prescription of the user and simply transmit the data thereof to the machining yard. It is enough for the optician's shop to only receive the machined lens. For this reason, the machining in the optician's shop is eliminated, and this largely reduces the load on the shop.
This invention is limited by the appended claims.

Claims

A method of manufacturing a pair of spectacle lenses, comprising designing a left lens and a right lens to satisfy requirements as to:

a) a user's prescription; and

b) minimizing a difference, or differences, in thickness and/or curvature, between said left lens and said right lens, so as to optimize balance between both lenses.
A method according to claim 1, comprising:

a step of adjusting a lens curve of an R1 surface of one of the right and left lenses having a relatively large R1 surface lens curve in relation to the other of the right and left lenses, to make the R1 surface lens curve of the one lens approximate to the R1 surface lens curve of the other lens.
A method according to claim 1, comprising:

a step of adjusting thicknesses of one of the right and left lenses having a relatively small central thickness and a relatively small edge thickness in relation to the other of the right and left lenses, to make those thicknesses on the one lens approximate to those thicknesses on the other lens.
A method according to claim 2 or 3, further comprising the step of insetting the right and left lenses into a spectacle frame.
A method according to claim 1, comprising:

a step of insetting the right and left lenses into a spectacle frame,

said designing step including:

a step of adjusting a lens curve of the R1 surface of each of the right and left lenses, to make those lens curves approximate to a frame curve of the front of the spectacle frame.
A method according to claim 1, comprising:

a step of insetting the right and left lenses into a spectacle frame,

said designing step including:

a step of adjusting lens curves of the right and left lenses by making a lens curve of the R1 surface of each of the right and left lenses approximate to a frame curve of the front of the spectacle frame and by making a relatively large lens curve of the R1 surface of one of the right and left lenses approximate to a relatively small lens curve of the R1 surface of the other of the right and left lenses; and

a step of adjusting thicknesses of one of the right and left lenses having a relatively small central thickness and a relatively small edge thickness in relation to the other of the right and left lenses, to make those thicknesses approximate to those thicknesses of the other lens.
The method according to any of claims 2 to 6, wherein each adjustment is performed based on a prescription of a user of the spectacles.
A method according to claim 1, comprising designing a left lens and a right lens to satisfy predetermined prescription requirements, comparing external characteristics of the lenses, and adjusting at least one of said external characteristics of at least one of said lenses if the difference in said at least one of said external characteristics between the lenses is greater than a predetermined threshold, whilst ensuring that the lens continue to satisfy said prescription requirements.
A method according to claim 1, comprising inputting data in keeping with said prescription into a transmitting device, transmitting said data to a remote lens manufacturing facility via an electronic data communications link, obtaining lenses to said requirements from said manufacturing facility and insetting said lenses in a pair of frames.
A system for supplying a spectacle lens, comprising:

a transmitting device installed on the side of transmitting data on spectacle lenses and a spectacle frame when manufacturing spectacles; and

an arithmetic device connected to said transmitting device via a communications line and installed on the side of machining the spectacle lens,

said transmitting device including:

a data transmitting unit for transmitting an item of spectacle frame data and a prescription to said arithmetic device,

said arithmetic device arranged to perform calculations so as to design the left and right lenses according to the method of claim 1 and including:

means for adjusting lens curves of the R1 surfaces of the right and left lenses in relation to each other;

means for adjusting lens thicknesses of the right and left lenses in relation to each other;

means for adjusting lens curves of the R1 surfaces of the right and left lenses in relation to the spectacle frame data; and

means for outputting these items of data.
A system according to claim 10, further comprising a polishing machine (8), grinding machine (9), and/or finishing machine which operates based upon data outputted from said means for outputting these items of data.